Inside-out hoops have diamonds on both the front and inside of the hoop. When someone looks at you, they see sparkle; when you look down, you see sparkle. More diamond surface area, higher price.
Front-facing hoops have diamonds only on the outside. Costs less, still looks great from normal viewing angles. Most people won't notice the difference in daily wear.
If budget matters, front-facing gives you more size for your money. If you want maximum impact, inside-out delivers.